Electrophotographic copying apparatus

ABSTRACT

An electrophotographic copying apparatus having a photoreceptor surface wound on a rotatory drum movable along a path relative to a plurality of actuable processing stations disposed along the path, in which apparatus the circumference of the photoreceptor drum is made as small as possible to an optically permissible extent so that two or more revolutions thereof completes one copying cycle with a rotatory metal cylinder forming a strong electrical field provided adjacent to a cleaning device for effective toner collection, thus contributing much to a compact size and light weight of the apparatus. The copying apparatus is further provided with a central suction device for efficient elimination of toner particles scattering in the apparatus, and heat or poisonous gases generated at various processing stations.

United States Patent Tanaka et a1.

1 1 Oct. 21, 1975 1 1 ELECTROPHOTOGRAPHIC COPYING [73] Minolta Camera Kabushiki Kaisha,

Osaka, Japan Filed: July 1, 1974 Appl. No.: 484,889

Assignee:

References Cited UNITED STATES PATENTS 1/1971 Howard et a1. 271/4 10/1971 Clarke et a1. 355/15 X 3,634,077 1/1972 Sullivan 15/115 X 3.635.555 1/1972 Kurahashi....... 355/8 3.767.300 10/1973 Brown et a1. 355/15 3.795.025 3/1974 Sadamitsu 355/15 X 3.819.261 6/1974 Ogawa l, 355/14 Primary ExaminerRichard L. Moses Attorney, Agent, or Firm-Wenderoth, Lind & Ponack [57] ABSTRACT An electrophotographic copying apparatus having a photoreceptor surface wound on a rotatory drum movable along a path relative to a plurality of actuable processing stations disposed along the path, in which apparatus the circumference of the photoreceptor drum is made as small as possible to an optically permissible extent so that two or more revolutions thereof completes one copying cycle with a rotatory metal cylinder forming a strong electrical field provided adjacent to a cleaning device for effective toner collection, thus contributing much to a compact size and light weight of the apparatus The copying apparatus is further provided with a central suction device for efficient elimination of toner particles scattering in the apparatus, and heat or poisonous gases generated at various processing stations.

9 Claims, 7 Drawing Figures ELI 59 -soonning returning 153 M1 L 5 9 t i 450 l 3139384542 a r US. Patent 0a. 21, 1975 Sheet 1 of4 3,914,046

scanning returning FIG. 3

US. Patent 0.21, 1975 Sheet 3 of4 3,914,046

FIG. 5

scanning FIG. 6

retummg lo I64 IE5 IE3 e 6765 o I26 US. Patent Oct. 21, 1975 Sheet 4 of4 3,914,046

FIG. 7

SOL2

ELECTROPHOTOGRAPHIC COPYING APPARATUS The present invention relates to a copying apparatus, and more particularly to improvements of an electrophotographic copying apparatus of xerographic system.

In recent years, there have been required smaller size devices in this type of xerographic apparatus. However, with the necessity of using the photoreceptor surface repeatedly in this type of apparatus. the toner powder remaining on the photoreceptor surface after the transferring operation must be removed and the removed toner particles suitably collected. Accordingly, devices for removing the residual toner, and filter bags for collecting the toner powder are required to be considerably large, resulting in large size and heavy weight of the apparatus.

On the other hand, the conventional photoreceptor drum has a minimum limit of approximately 120 mm in diameter, which fact greatly hinders thereduction of the size of apparatus.

Furhtermore, in the conventional copying apparatus of the above described type, since developing material in the form of powder comprising toner particles and carrier material is employed, there are cases where the toner particles separated from the carrier material scatter or float in the apparatus, consequently soiling the latter, or in the worst cases, leak out of the apparatus, resulting in the staining of the interior of the room in which the copying operation is carried out.

There has been another problem with such a conventional apparatus in that ozone is generated at various parts due to the high voltage power required for the operation of the various processing devices such as charging, transfer, discharging and collection of toner powder, or that heat and gases are produced in fixing the toner powder image on the copy paper sheet at high temperatures, also resulting in atmospheric pollution in the room.

Accordingly, as essential object of the present invention is to provide an electrophotographic copying apparatus which is compact in size and is relatively light weight with a substantial elmination of the disadvantages inherent in the conventional copying apparatus.

Another important object of the present invention is to provide a copying apparatus of the above described type which eliminates soiling both inside and outside of the apparatus without any possibility of atmospheric pollution due to exhausted air from the apparatus.

A further object of the present invention is to provide a copying apparatus of the above described type which is comparatively simple in construction, easy to maintain and provides accurate copying performance.

According to the copying apparatus of the present invention, a metal cylinder with a corona discharger enclosed therein is rotatably provided adjacent a cleaner brush for removing residual toner particles on the photoreceptor drum at a position between said cleaner brush and a filter section communicated with a central suction device, so that most of the toner particles removed from the photreceptor surface are attracted and collected on the surface of the metal cylinder which forms a very strong electrical field with only a very small amount of air entrained toner particles filtered out at the filter section, by which procedure the filter bag conventionally occupied a large space can be made much smaller in size.

Moreover, in the copying apparatus of the present invention, the photoreceptor drum is made as small as possible in diameter to an optically permissible extent so that two or more revolutions thereof completes one copying cycle. This contributes much to the compact size of the apparatus together with the above described provision of the metal cylinder for toner collection.

Furthermore, another important feature of the present invention is that the apparatus is equipped with a central suction device associated with the filter section which advantageously attracts and eliminates toner particles scattering in the apparatus, heat arising from a fixing device or exposure lamp, poisonous gases generated in a fixing device, or ozone produced at various parts of the apparatus.

These and other objects and features of the present invention will become apparent from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, in which;

FIG. I is a schematic diagram showing a sectional side view of a copying apparatus according to the present invention.

FIG. 2 is a perspective view of a copy paper sheet feed mechanism employed in the apparatus of FIG. I,

FIG. 3 is a side elevational view of the copy paper sheet feed mechanism of FIG. 2,,

FIG. 4 is a similar view to FIG. I, but particularly shows relation between a suction device and various processing devices,

FIG. 5 is a perspective view of the suction device, on an enlarged scale, with a filter and second section containing active carbon withdrawn from the suction device,

FIG. 6 is a similar view to FIG. 1, but particularly shows the driving system thereof, and

FIG. 7 is an electrical circuit diagram illustrating various elements of the copying apparatus according to the present invention.

Before the description of the present invention proceeds, it is to be noted that like parts are designated by like numerals throughout the several views of the accompanying drawings.

Referring to FIG. 1, the electrophotographic copying apparatus according to the present invention generally comprises a photoreceptor drum 1 having a photore ceptor surface 10 on the outer periphery thereof rotatably mounted at approximately the central part of the apparatus housing T onto a shaft journaled in the frames of said housing T to rotate in the direction indicated by the arrow so as to cause the photoreceptor surface la sequentially to pass various processing stations, such as a charging station having a charger 2, an exposure station with an exposure adjusting plate 6, a developing station A, a transfer station provided with a transfer charger 35, and a drum cleaning station having a residual toner removing device C, each station being disposed along the path of the photoreceptor surface la, A movable transparent platform 3 on which an original 4 to a copied is placed is reciprocatingly supported above said photoreceptor drum 1 at an upper part of the apparatus T. A main light source L for illuminating the original 4 is provided below and adjacent to the platform 3, and an optical mirror and lens system projects light rays from the original 4 onto the photoreceptor surface la.

The photoreceptor drum 1 further comprises the clectrophotosensitive photoreceptor layer In which is composed either of a thin film layer of noncrystalline Se alloy for example. approximately 0.2;; to 2p. in thickness laminated with an organic semiconductive layer of PVK etc,.( for example, approximately p. to 25p. in thickness or of a single layer of non-crystalline Se alloy for example. approximately 2011, to 601.4. in thickness suitably applied. so as not to form a junction, onto the outer periphery of a cylindrical drum lb made of, for example, aluminum, stainless steel etc.. or of plastic etc.. which has a surface layer of thin film formed by plating or vacuum deposition of aluminum. chromium. palladium etc., the diameter of the drum 1 being comparatively small for example. approximately 50 to 100mm Although it is conventionally considered that the minimum limit of the photoreceptor drum diameter is approximately 120mm, the present inventor confirmed. after a series of experiments and trial production. that a drum with a small diameter in the range of 50 to 100mm can efficiently perform copying operations without any distortions of optical images, and he then developed the drum of the present invention, after taking into considerations the relation of the drum to various processing devices mentioned later, which contributes greatly to the smaller size of the apparatus.

A charger 2 for changing the photoreceptor surface la mounted adjacent to and above the photorecepter surface la is adapted to effect a corona discharging of a polarity which is suitable for the charging characteristics of the photoreceptor surface la thereby to a sequentially charge the surface la during rotation of the photoreceptor drum 1.

The upper surface of 2' of the charger casing is formed as a wire mesh, behind which an erasing lamp El is suitably mounted to erase unnecessary charge on the photoreceptor surface la.

The photoreceptor surface la charged as described above is subsequently exposed to light at the exposure station.

The optical system for exposure includes the exposure lamp L which is suitably mounted adjacent to and below the movable transparent platform 3 at the upper right portion of the apparatus T for projecting light onto the original 4 directly or through a mirror Ml having a surface of second degree; and a second mirror M, fixedly provided below the platform 3 and inclined at approximately 45 with respect to the lower surface of the platform 3 for directing the light rays from the original 4 to a lens 5 enclosed in a lens tube 5' which is suitably fixed to the frame of the apparatus at the left of the mirror M The lens tube 5' has a mirror M at one end thereof, so that the light rays from the mirror M, are further directed through the lens 5 to a fourth mirror M which faces the lens 5 and is suitably inclined to transmit the light rays in turn to a fifth mirror M fixedly mounted below and parallel to the mirror M at a position close to the photoreceptor surface la. The light rays reflected by the fifth mirror M,. are projected onto the photoreceptor surface la through the exposure adjusting plate 6 which is pivotally mounted to the apparatus T for adjusting the amount of exposure.

In the case described above. the platform 3 and the photoreceptor drum 1 are adapted to move or rotate respectively at an equal speed in the direction of arrows in FIG. 1. Accordingly, a stationary light image of the original 4 is adapted to be projected onto the photoreceptor drum 1.

Thus. the portion on the photoreceptor surface la formed with an elctrostatic latent image by the light 5 rays reflected from the original 4 reaches the developing station as the photoreceptor drum 1 rotates and is developed into a visible toner powder image by the devloping device A The developing device A extends across the width of O the photoreceptor surface la and is substantially enclosed in a housing A] except for an opening adjacent to the photoreceptor surface la whereat the development of the latent image is effected, and an opening A,

in which a toner bottle 16 is received to replenish the 5 toner powder depleted from the developer material during development of the latent image. The developing roller 7 extending the width of the housing Al comprises a rotatable outer cylinder 70 of a non-magnetic material such as aluminum or brass with the outer periphery thereof provided with minute convex and concave portions to increase friction.

Inside the outer cylinder 7a, three elongated permanent magnets 9, l0 and 11 are disposed on a stationary bar 8 at approximately right angles to one another with the magnets 9 approximately facing the axis of the photoreceptor drum 1 so that the magnetic force fields of the magnets 9, l0 and .11 intersect to effect formation of magnetic bristles of developer material upon the roller 7. The outer cylinder 7a enclosing the bar magnets 9, 10 and H therein is suitably journaled at its ends on the side walls not shown of the apparatus so as to be rotatable counterclockwise about the stationary bar 8 in the same direction as the drum 1.

A sump A for developing material comprising toner powder and carrier material is provided at the bottom portion of the housing A adjacent to the outer cylinder 70.

Thus, the developing material is attracted to the surface of the developing roller 7 by the action of the mag net 10 and raised as the developing roller 7 rotates to form magnetic brush bristles at a position of the magnets 9, which brush bristles lightly rub against the photoreceptor surface la so as to develop the latent image into a visible toner powder image.

The developing material which has been used for developing is further carried by the attracting force of the permanent magnet l l as the developing roller 7 rotates and is scraped off the surface of the developing roller 7 by a scraper l2, and the scraped developing material falls onto a stirring roller 13 rotatably mounted adjacent to the scraper 12: while the toner powder which has been controlled properly in quantity by the toner dispenser 14 mounted above the stirring roller 13 also falls onto the stirring roller 13. Thus the developing material and the toner powder are mixed and stirred effectively through the rotation of the stirring roller 13.

As described above. the toner concentration in the developing material is kept approximately at a constant level in preparation for the subsequent copying operations.

A closely wound spring-like member, for example, a coil spring [5 with the neighboring turns thereof contacting with each other in its normal contracted state. is suitably provided below and in contact with a slit 14' formed at the bottom portion of the toner dispenser 14. By properly expanding the spring 15, gaps are formed between the neighboring turns of the spring [5 through which controlled amount of toner powder is adapted to be supplies. The expansion or contraction of the spring is effected by a cam mechanism or the like not shown associated with the rotation of the drum 1, i.e., corresponding to copying operation for each copy paper sheet.

The larger toner bottle 16 provided above the toner dispenser 14 is effective for continuous replenishment of toner powder for a long period of time and also for easier maintenance and handling of the apparatus.

The bottle 16 can be replaced with a new bottle by rotating, through an angle of 90, a side plate 17 pivotally provided on the side wall of the toner dispenser 14 to an opened position shown by the dotted line in FIG. 1, and placing a new bottle on the plate 17, which is then rotated back to the original closed position.

There is an opening S in the side wall of the developing device A which is communicated, through a duct 54, with a suction device 142 mentioned later FIGS. 4 and 5 thus of the interior of the developing device A or resultant leakage of any toner particles to the outside of the apparatus is effectively prevented without any toner particles scattering in the developing device A.

A cover plate 18 which is pivotally provided adjacent to the sump A at the bottom of the developing device A is adapted to be opened or closed for the exchange of the developing material after a predetermined number of copying operations.

As described hereinabove, the photoreceptor surface 1a bearing the toner powder image developed by the developing device A further reaches the transfer station as the drum 1 rotates, whereat the copy paper sheet is supplied as described hereinafter.

Referring now to FIGS. 2 and 3, the sheet feed mechanism P includes a tray 21 for holding a supply of cut copy paper sheets for automatic paper feeding; feeding rollers 20 with associated devices for separating a single sheet of copy paper from the top of the stack of copy paper sheets on the tray 21; and a guide table 23 for manual insertion of the copy paper sheet which has depending sides 23a extending downward and which is pivotally connected at one end of said sides 23a to the side walls of the apparatus T by a pair of pins 23', so as to be opened into a roughly horizontal position over the tray 21 for the manual insertion or closed into a vertical position shown by a chain line in the drawings in the case of automatic paper feeding.

The guide table 23 is provided with a pair of L- shaped guide plates 24 movably mounted on the sur face of the plate 23 so that the distance between the guide plates 24 can be adjusted according to the sizes of the copy paper sheets.

A pair of special arms 25 are provided on opposite sides of the guide table 23. Each of the special arms 25 further comprises a first arm 26 and a second arm 27 which are pivotally connected to each other by a pin at one end so that the arm 25 can be folded about the pin 30. The other end of the first arm 26 is pivotally connected to the side 23a by a pin 28 at approximately the middle portion of the latter, while the second arm 27 has its other end pivotally connected to the side walls of the appratus T by a pin 29. The above end of the arm 27 is further extended downward to some ex tend to form a projection 27a, thus the arm 27 is formed roughly in the shape of 1... A small projection 26a formed on the arm 26 at the injunction between the arms 26 and 27 is adapted to engage the upper edge of the arm 27 and prevents the arm 25 from being folded downward further at its fully straightened position, allowing the latter to be folded only upward, i.c., in a direction to close the guide plate 23.

A pair of rotating arms 31 are provided on the outer surfaces of opposite side walls of the apparatus adjacent to the L-shaped arms '27, each of said arms 31 is pivotally connected, at the upper portion thereof, to the side wall of the apparatus by a pin 32 and is urged toward the right in the drawings by a tension spring 33 extented between the middle portion of said arm 31 and the side wall of the apparatus, while the rightward movement counterclockwise rotation about the pin 32 of the arm 31 is limited by a stopper 33a fixed to the side wall. The lower end of the arm 31 rotatably supports a shaft 104 for feeding rollers 20, while the upper end 31b thereof faces the projection 27a of the arm 27 so that upon rotation of the arm 27, the projection 27a engages the upper end 31 b of the arm 31.

The rotatable shaft 104 for the feeding rollers 20 has friction rollers 105 and 133 adjacent to its one end and a pair of separating rollers 20 in its middle portion, each fixedly mounted on said shaft 104.

A guide roller 22 is rotatably mounted on a shaft 22a suitably journaled on the side walls of the apparatus and is adapted to contact the feeding rollers 20 when the guide table 23 for manual operation is opened into the horizontal position so that a copy paper sheet can be inserted between the rollers 20 and 22.

Accordingly, in the case of automatic paper feeding where the guide table 23 for manual insertion is closed into the vertical position, the arms 26 and 27 constituting the special arms 25 are folded about the pins 30 with the special arms 25 rotating clockwise about the pins 29 and subsequently the projections 27a of the L- shaped arms 27 are disengaged from the upper ends 31a of the rotating arms 31, with the arms 31 rotating counterclockwise about the pins 32 by the tension of the springs 33 and stopped by the stopper pins 33a.

Accordingly, the friction roller 105 fixedly mounted on the rotatable shaft 104 for feeding rollers 20 contacts a friction roller 103 which in turn contacts another friction roller 101 fixedly mounted, together with a sprocket 98, on a ratable shaft 96 mentioned later, and the driving force transmitted by a chain 100 thus rotates the roller and the shaft 104, which in turn rotates the feeding rollers 20 contacting the copy paper sheet at the top of the stack on the trap 21 so as to forward the copy paper sheet toward the photoreceptor drum 1.

In the case of manual insertion of the copy paper sheet, the guide table 23 is opened to its horizontal position with the special arms 25 fully straightened and the L-shaped arms 27 rotated counterclockwise about the pins 29, thus causing the projections 27a of the arms 27 to contact the upper ends 31b of the rotating arms 31 and consequently to rotate the arms 31 about the pins 32 against the tension of the spring 33. In this state, the friction roller 105 is disengaged from the friction roller 103 and a friction roller 133 fixedly mounted on the same rotatable shaft 104 as the roller contacts another friction roller 131 fixedly mounted on a rotable shaft 97 together with a sprocket 99 with the feeding rollers 20 contacting the roller 22.

Accordingly, the driving force is transmitted to the feeding rollers 20 through the chain 100, the sprocket 99, the friction rollers l3l and 133, and also the shaft 104 to rotate the rollers 20 in the direction of arrow, so that the copy paper sheet can be forwarded toward the drum 1 when inserted between the rollers 20 and the roller 22.

As described above, upon closing ofa printing switch SW, the separating rollers 20 starts rotating. separating the single copy paper sheet from the top of the paper stack on the tray 21 with the copy paper sheet transported through a pair of feeding rollers 34 FIG. I toward the tranfer station.

A microswitch MSF disposed along the path of the copy paper sheet between the rollers 34 and the transfer station FIG. 1 is adapted to be actuated as the copy paper sheet passes along the above path and stops the feeding rollers 20, after which the copy paper sheet is transported by the rotating of the rollers 34 toward the drum 1.

Referring back to FIG. I, the toner powder image formed on the photoreceptor surface la as described earlier is brought into contact with the copy paper sheet with the toner image transferred onto the copy paper sheet by means of the transfer charger 35 disposed below the photoreceptor surface la.

Polarity of the voltage to be impressed upon the transfer charger 35 may be one which will substantially attract the toner particles. For example, for the posi tively charged toner particles, transfer can be effected by a negative voltage direct current, a pulsating current, or an A. C. corona charger, in which later case, transfer is also effected, since the A. C. corona charger substantially supplies a negative current, based on the difference in mobility of positive and negative inons.

Since the casing 35' of the transfer charger 35 is formed in a concave shape, the developing material, particularly the carrier from the developing device A, may accumulate therein. When this accumulation is left as it is, spark discharges, may result so that it is desirable that the casing 35 may be open at its bottom or be of wire mesh construction as shown in FIG. 1.

In effecting the manual insertion of the copy paper sheets, the guide table 23 is open into the horizontal position and the copy paper sheet is inserted between the rollers 20 and 22 with the leading edge of the copy paper sheet depressing a micro-switch MSP too start the copying cycle.

Thus, the copy paper sheet on which thetoner powder image has been transferred reaches a separating position provided with a separating piece 36 pivotally mounted on the apparatus through the rotation of the photoreceptor drum 1. In this state, the copy paper sheet closely adheres electrostatically to the photoreceptor surface la. However, as the photoreceptor drum 1 is of a small diameter, the resilience of the copy paper sheet works effectively to cause some clearance be tween the leading edge thereof and the photoreceptor surface la, so that the separating piece 36 which is adapted to lightly contact the photoreceptor surface la is inserted into the clearance as the drum 1 rotates. Since the separating piece 36 is adapted to turn downwardly by about 30 about the pivoted point thereof, namely, counterclockwise at a position to 7 mm from the leading edge of the copy paper sheet, the sheet is positively peeled off the photoreceptor surface la with the rotation of the drum 1, after which the separating piece 36 is turned back to its original position.

The separated copy paper sheet is attracted by a suction conveyer device 37 of a suction belt type, and is carried in the direction of an arrow by a belt 38 sup ported by three rollers into a fixing device B.

At this time, the electric charge remaining on the copy paper sheet is adapted to be erased by a paper discharger 39 mounted above the suction conveyer device 37, whereby attraction between copied paper sheets can be avoided when the copied paper sheets are overlapped or stacked after the transferring.

Thus, the electrically discharged copy paper sheet with toner powder image transferred thereon is fed between an upper heater 40 and lower heaters 42 of the fixing device B, in which the toner powder image is fused and fixed on the copy paper sheet.

Since the above fixing by heat required a large amount of heat, thermal efficiency of the fixing device B should be fully taken into consideration, employing materials with little heat transmission to other parts as well as rapid heating property. For example, the above heater 40 included an aluminum reflecting shade 41 having a surface of second degree with high reflecting efficiency for heat rays, and the lamp-type heater 40 projecting near-infrared rays disposed in the shade 41 which has, at the lower opening thereof a wire mesh 43 of small heat capacity for example, steel wire mesh of approximately 200 to 400 meshes having a portion for the infrared rays to pass through and another portion which will radiate infrared rays of long wave length after converting the absorbed infrared rays.

On the other hand, since the heating from the reverse side of the copy paper sheet has an important effect to the fixing of the toner powder image, the lower heaters 42 similar in construction to the above upper heater 40 are disposed below the copy paper sheet, said heaters 42 are surrounded with a reflecting shade 45 having, at the opening thereof facing a copy paper sheet, a wire mesh 44 similar to the upper wire mesh 43.

Walls 46 and 47 which are of insulating materials such as asbestos, etc. are disposed to surround the heater 40, the reflection shade 41, the heater 42, and the reflecting shade 45 thereby preventing the heat from being radiated outside the fixing device B.

Thus, after the toner image on the copy paper sheet is heated and fixed on the copy paper sheet in the fixing device B the copied paper sheet is discharged onto a tray not shown by rollers 48.

On the other hand, since, a small quantity of of toner powder amounting to l0 to 50 of the toner powder used in developing remains on the photoreceptor surface In after completion of transfer with the electric charge impressed by the transfer charger 35 remains on the surface la, this must be removed from the surface la. For this purpose, an erasing lamp EL, for erasing the electric charge is adapted to project light onto the photoreceptor surface la after the copy paper sheet has been peeled off.

It has been confirmed that the application of light by the erasing lamp EL amounting to several times the light amount employed in exposing the light image by the exposure lamp L permits the charge erasing of the portion on the photoreceptor surface 1a which is behind the remaining toner image.

Thus, the toner particles remaining on the surface of the photoreceptor surface la with less electrical attraction reach the cleaning station through the rotation of the photoreceptor drum 1 so as to be cleaned by the cleaning device C.

Referring to FIGS. 1 and 4, the residual toner removing device C extending across the width of the photoreceptor lb generally comprises three sections communieating with one another, a cleaner section C, including a cleaner brush 49 rotatably mounted in a housing 52, and an intermidiate section 53 extending from the housing 52 and communicating, through a duct 54, with a filter section 55 having a suction device 142 suitably connected thereto (FlG. 4

In the cleaner section C the housing 52 is provided with an opening facing the photoreceptor surface la with the upper and lower edges of the opening slightly spaced away from the surface la to form gaps for air passage. The cleaner brush 49 having brush bristles 49a of animal fur such as rabbit fur, synthetic furs such as Teflon, polyester, nylon acrylonitrile secured to the entire outer periphery thereof is rotatably supported close to the above opening so that the brush bristles 49a slightly rub against the surface la as the drum 1 and the cleaner brush 49 rotate in the directions indicated by the arrows. A convex upper casing plate 51 which is electrically insulated from the housing 52 is provided above the brush 49 so as to partially cover the brush 49 with tips of the brush bristles 49a contacting the plate 51 to a certain extent.

Accordingly, the toner particles remaining on the photoreceptor surface la are wiped off the surface la as the drum 1 and the cleaner brush 49 rotate, caught in the brush bristles 49a, and dislodged from the bristles 49a when the latter strike against a flicker rod 50 fixedly provided in a path of the brush bristles 49a at a position between the rear edge of the upper casing 51 and the bottom plate of the housing 52. in order to prevent the detached toner particles from adhering back to the bristles 49a and thus avoiding deterioration of the bristles 49a, the above upper casing plate 51 and the flicker rod 50 are made, for example, of brass etc., so that, upon contact with the bristles 49a, the plate 51 and rod 50 are charger with frictional electricity with the same polarity as that of the toner particles, thus effectively repelling the toner particles therefrom which are further sucked into the filter section 55 by the air flow caused by the suction device 142.

A metal cylinder 57 with a corona discharger 56 enclosed therein is rotatably mounted in the intermediate section 53 for collecting the detached toner particles.

Since a very strong electric field is formed between the intermediate section 53 and the metal cylinder 57 by the corona discharge from the corona discharger 56 for example, if a votage of 7.5 KV is impressed with a gap of 25 mm between the discharger 56 and the metal cylinder 57, the voltage on the metal cylinder 57 is increased by b 4.5 KV 95 to 98% of the removed toner particles are electrically attracted onto the surface of the metal cylinder 57, which are further scraped off the surface of the latter by a doctor blade 58, for example, of polyurethane rubber disposed to contact the surface of the cylinder 57 and collected in a sump 59 provided below the cylinder 57. The air still containing a small amount of toner particles is further sucked into the filter section 55 by the suction force of the suction device 142 through the duct 54, whereat the toner particles are completely filtered out (FIG. 4).

Due to the fact that most of the removed toner particles are collected by the cylinder 57 with only a small amount of remaining toner filtered in the filter section 55, the filter section 55 can be of very small capacity (in the range of one-twentyth to one-fiftyth of the conventional device), resulting in a compact size of the apparatus T.

Furthermore, the toner particles attracted on the cyl inder 57 are electrostatically selected for polarity with only toner particles having desirable characteristics collected on the cylinder 57, which fact enables the toner particles pooled in the sump 59 to be economically re-used.

According to the present invention, although the photoreceptor drum 1 is adapted to rotate more than 2 times per one copying cycle since the circumference of the drum 1 is shorter than the full length of the original to be copied, no inconvenience results therefrom as the drum 1 is formed to be endless without any junction.

Referring now to FIGS. 4 and 5, the central suction device 142 associated with the filter section 55 for eliminating the toner particles, heat and gases generated at various parts of the apparatus T will be described hereinbelow.

Referring particularly to FIG. 5, a bellow type pipe is led from the suction conveyer device 37 for the copy paper sheets mentioned earlier, while the other bellow type pipe 141 is led from the opening S formed in the side wall of the developing device A (FIG. I), each being tightly connected to the duct 54 at the other end thereof.

The filter section 55 further comprises a first section 550 to which the duct 54 is communicatingly connected, and a second section 55b which is in communication with the suction device 142.

A part 143 of the under surface of the first section 55a facing the fixing device B and another part 144 at the left side wall of the front section 55a adjacent to the exposure lamp L are each composed of a wire mesh element, through which the heat with high temperatures generated in the fixing device B and the heat arising from the exposure lamp L are absorbed into the second section 55b by the suction force from the suction device 142 so as to prevent high temperatures from being transmitted to other parts of the apparatus T.

Furthermore, in the above first section 550, a filter 145 composed, for example, of polyester wool of about 50 to 200p. in diameter or of polypropylene wool formed into a plate with more than 30mm thickness is replaceably attached. In cases where heat resistance is particularly required, glass wool is preferably employed.

On the other hand, the above second section 55b has two side walls of wire mesh 146 and 147, of for example, stainless steel or brass wire mesh with I00 to 400 meshes plated or coated with white gold, gold, silver, copper or oxides of silver or copper which are effective catalysts for the reduction of ozone, or are further plated or coated with manganese dioxides or lead peroxides; one of said wire mesh walls 147 is in communication with the first section SSa, while the other wire mesh wall 146 is disposed adjacent to the suction device 142 with the charger 2, the transfer charger 35, and the paper discharger 39 etc., connected to the second section 55b by pipes (not shown).

The second section 55b contains approximately 100 to 300 g of granular active carbon 148 with diameter of 2 to 3 mm so as to absorb minute toner particles less than 2 to 3p. in diameter still remaining in the air after passing through the filter 145 of the first section 55a.

The above filter 145 and the active carbon 148 are adapted to be always kept in good condition by replac ing them after a predetermined period of time.

Accordingly. toner particles scattering or floating in the developing device A. those removed by the clean ing device C, or those floating in various parts of the apparatus T (FIG. 4) and the heat arising from the fixing device B and the exposure lamp L, or the poisonous gases generated in the fixing device B are adapted to be completely absorbed and eliminated by the filter 145 provided in the section 55a and the active carbon 148 contained in the section 55b as the former pass through the latter with only perfectly clean air free from toner particles or poisonous gases being discharged from the suction device 142, thus protecting the atmosphere in the room from any pollution,

Meanwhile, the ozone gas generated by the charger 2, the transfer charger 35 and the paper discharger 39 etc, is reduced to oxygen when passed through the wire meshes I46 and 147 of the second section 55b by the reducing action of white gold, gold, or silver plated or coated on the meshes 146 and 147 and discharged from the suction device 142, whereby leakage of ozone gas which may be poisonous to human bodies is per fectly prevented.

Furthermore, as shown in FIG. 4, if a baffle plate 150 is provided extending upwardly, approximately half way in the filter section 55 at right angles from the bottom portion of the latter with one surface of the plate 150 facing the duct section 54 so that the air entrained toner particles passing through the duct 54 collide with the baffle plate 150, most of the toner particles will fall and be collected at the front lower part of the plate 150, thus limiting the soiling of the filter 145 and consequently prolonging the life of the filter 145.

A driving mechanism of the present invention will be described below with reference to FIG. 6.

A bevel gear 62 fixedly mounted on one end of a shaft 60 of a main motor MM engages a bevel gear 64 secured to a shaft 63 rotatably provided at right angles to the driving shaft 60.

A chain 87 is directed around a sprocket wheel 65 secured to the shaft 63 together with a sprocket 66, a sprocket wheel 68 secured on a paper feeding roller shaft 67 for the paper feeding rollers 34, a sprocket wheel 70 secured on a rotatable shaft 69 of the stirring roller 13 for stirring the developing material inside the developing device A, a sprocket wheel 72 secured on a rotatable shaft 71 of a paper feeding clutch 94, a sprocket wheel 74 secured on a photoreceptor drum driving shaft 73, a sprocket wheel 76 for changing direction fixedly mounted on a rotatable shaft 75, a sprocket wheel 78 secured on a rotatable shaft 77 of a clutch 121 for returning the platform 3, a sprocket wheel 80 secured on a rotatable shaft 79 of a clutch 122 for advancing the platform 3, a sprocket wheel 82 secured on a driving shaft 81 of the toner collecting metal cylinder 57 for the cleaner brush 49, a sprocket wheel 84 secured on a feeding roller driving shaft 83 for feeding the copied paper sheet into the fixing device B, and a sprocket wheel 86 secured on a belt driving roller shaft 85 for the suction conveyer device 37. The chain 87 is driven in the direction of the arrow by the main motor MM for imparting rotation of the above shafts 67, 69, 71, 73, 75, 77, 79, 81, 83 and 85. On the other hand, a chain is directed around the sprocket wheel 66 secured on the shaft 63 and a sprocket wheel 89 secured on a developing roller driving shaft 88 of the developing device A. and this chain 90 is adapted to rotate in the direction of its arrow by the main motor MM. Since a gear 91 secured parallel to the sprocket 89 on the developing roller driving shaft 88 engages a gear 93 secured on a rotatable shaft 92 of the outer cylinder 70 for the developing device A, the rotational force is imparted to the latter so as to rotate the cylinder 7a in the direction of the arrow,

A sprocket wheel 95 is secured in parallel to the sprocket wheel 72, through the paper feeding clutch 94, on the shaft 71 for the paper feeding clutch 94 with the chain (FIGS. 2 and 6) directed around the sprocket wheel 95, and the sprocket wheels 98 and 99 which are secured respectively on the paper feeding roller driving shafts 96 and 97, so that when the paper feeding clutch 94 is engaged, the chain 100 is adapted to be driven in the direction of the arrow. In the automatic paper feeding operation, the paper feeding roller 20 is adapted to rotate through a friction roller 101 secured in parallel to the sprocket wheel 98 which is secured on the paper feeding roller driving shaft 96, a friction roller 103 secured on a shaft 102 rotatably mounted on the apparatus T, and also a friction roller 105 secured on the paper feeding roller shaft 104.

On the other hand, in the manual insertion of copy paper sheets, by bringing the paper feeding roller supporting arms 31 to a position shown by dotted lines, the paper feeding rollers 20 are adapted to rotate through a friction roller 131 secured in parallel to the sprocket wheel 99 on the paper feeding roller driving shaft 97, and a friction roller 133 secured on the paper feeding roller shaft 104.

Rotation of the paper feeding roller 20 is adapted to be controlled by the operation of the paper feeding clutch 94 by a print switch SW and a group of switches mounted in a moving path of the platform 3.

A chain is directed around a sprocket wheel 107 secured on a feeding roller shaft 106 for the copy paper sheet and a sprocket wheel 109 secured on a delivery roller shaft 108. The chain 1 10 is adapted to be rotated in the direction of the arrow by the main motor MM through a coupling gear 111 secured in parallel to the sprocket wheel 84 on the feeding roller driving shaft 83 and a gear 112 secured in parallel to the sprocket wheel 107 on the feeding roller shaft 106.

On the other hand, the photoreceptor drum 1 is adapted to rotate in the direction of the arrow by the main motor MM through a gear 113 secured in parallel to the sprocket wheel 74, which is secured on the photoreceptor drum driving shaft 73, and a gear 115 secured on the photoreceptor drum. Small balls (not shown) are provided on the under surface of the platform 3 and the upper portions of the side walls of the apparatus T, the upper portons of the side walls of the apparatus T thereby to supporting the platform 3 for reciprocal motion with stoppers provided on opposite ends of the rails (not shown) for preventing disengagement of the platform 3. Furthermore, a rack 118 is fixedly provided parallel to the V-groove rails (not shown) at the under surface of the platform 3. Said rack 118 is sufficiently long to engage a platform driving gear 117 secured on the platform driving shaft 116 during the movement of the platform 3.

The platform driving gear 117 secured on the rotatable platform driving shaft 116 is adapted to rotate in a direction shown by the real line by a gear 1 19 secured on the rotatable shaft 79 through a platform advancing clutch 122, and also in a direction shown by the dotted line by a gear 120 secured on a rotatable shaft 77 through a platform returning clutch 121 Thus, the plat form 3 is adapted to move in a scanning direction and a returning direction respectively by the rack 118 and the gear 117. Since the chain 87 is directed around the sprocket wheel 80 secured on the shaft 79 and the sprocket wheel 78 secured on the shaft 77, the sprocket wheels 80 and 78 rotate in opposite directions to each other. The advancing and the returning of the platform 3 are adpated to be controlled by the print switch SW and the group of switches mounted in the moving path of the platform 3.

As the pitch diameter of the gear 120 for returning the platform 3 is larger than that of the gear 119 for advancing the platform 3 in the scanning direction, returning of the platform 3 to the original starting position can be performed quickly.

The toner collecting metal cylinder 57in the cleaning device C is adapted to rotate by the main motor MM through a gear 123 mounted integrally with the sprocket wheel 82 which is secured on the roller driving shaft 81, and a gear 125 secured on a toner collecting roller shaft 124.

On the other hand, a cleaner brush 49 is adapted to be rotated by a belt 132 directed around a pulley 126 secured to the other end of the driving shaft 60 for the main motor MM, a direction changing pulley 128 rotatably mounted on an intermediate shaft 127, and a pulley 130 secured on a cleaner brush driving shaft 129.

Subsequently, an electrical control circuit of the apparatus of the present invention will be described hereinafter with reference to FIG. 7.

First, upon closure of a main switch MSW, a current flows to a pilot lamp PL, a suction fan FA for the suction device, and the fixing device B. But at this time, the fixing device B which is connected in series to a temperature controller TC is adapted to be operated by the temperature controller TC.

Upon depressing of the print switch SW, a relay RL. is energized and is self-retained by a relay contact is Simultaneously, a relay RL, is energized through a relay contact 18 and is self-retained by a relay contact 25: thereby to actuate a main motor MM, a charge erasing lamp EL,, and a low voltage power source LT and high voltage power source HT.

At this time, the high voltage power source HT is adapted to supply power to processing devices such as the charger 2 for charging, the charger 35 for transferring, the discharger 39 for paper charge erasing and the corona discharger 56. The low voltage power source LT is a power source for developing bias.

Thus, the exposure lamp L is lighted by the current through the contact of the relay RL and the clutch 122 for driving the platform 3 in the scanning direction is actuated by the current through a contact 18 whereby the platform 3 starts moving in the direction of scanning. At the same time, the paper feeding clutch 94 is also atuated by the current through the contact 18;,, whereby the feeding operation of the copy paper sheet begins. When the leading edge of the advancing copy paper sheet depresses the movable contact arm of a microswitch MSF disposed in the path of the copy paper sheet, the microswitch MSF is opened and the paper feeding clutch 94 stops its operation.

Also, a projection Ta fixedly mounted on the platform 3 moves as the platform 3 advances in the scanning direction and closes a normally open microswitch M8 provided in the path of the projection Ta at such a position that the mocroswitch M5 is actuated by the projection Ta in timed relation to the separating piece 36 for the copy paper sheet when the tip of the separating piece 36 is inserted by 5 to 10mm from the leading edge of the copy paper sheet. Thus, upon closure of the switch MS a solenoid SOL is energized to actuate the separating piece 36 for the separation of the copy paper sheet form the photoreceptor drum 1 (FIG. 1). When the projection Ta has passed the microswitch M8 the current flowing to the solenoid SOL: is cut off to cause the separating piece 36 to return to the original position by the urging force ofa spring (not shown).

The projection Ta further advances to contact a microswitch MS movably provided for copy size determination, which has been set to the size of an original or a desired copying size, thereby to open the contact of the switch M8 Accordingly, the self-retaining of the relay RL, is released to turn off the exposure lamp L with the contact 18 of the relay RL is switched to deenergize the clutch 122 for advancing the platform 3 and to energize the clutch 121 for returning the platform 3.

Accordingly, the platform 3 starts moving in the direction of returning. At the same time, an erasing lamp EL is lighted by the current through a contact 18, of the relay RL,. At this time, since the charger 2 for charging is still in its operative condition, and the developing roller 7 is also driven through the main motor MM, the development of the unnecessary portion of the photoreceptor drum 1 is prevented without waste of toner powder and unnecessary load upon the cleaning device C.

Although the platform 3 with the projection Ta further continues its movement in the direction of return' ing, the microswitch MS, does not function even if it is depressed by the projection Ta since the switch MS has already been actuated as described above with the circuit opened.

Thereafter, the platform 3 returns to a predetermined position to actuate a microswitch MS for energizing a relay RL Accordingly, the electric charge in a capacitor C charged through the contact 35, is discharged to generate a pulse signal to start the operation of a timer relay TR.

As is clear from the above description, since the group of switches M5 MS: and MS; etc., adapted to be operated by the movement of the platform 3 to control the starting and stopping of each processing device constituting the copying apparatus, simple control of the apparatus can be effected with high accuracy.

The timer TR is adapted to operate only at the time of one sheet copying, and is set to a time required for the copy paper sheet of maximum size to be delivered out into the tray (not shown).

Thus, as the timer relay TR disconnects the circuit for the relay RL at pre-set time, the self-retaining of the relay RL, is released with the main motor MM, the charge erasing lamp EL,, the low voltage power source LT, and the high voltage power source HT deener gized, and thus the copying apparatus finishes one copying cycle thereby to resume its stand-by condition.

Subsequently. a continuous copying operation of many copy paper sheets will be described hereinafter.

A portion surrounded by dotted lines in the FIG. 7 functions as a sheet counter, in which a switch CSW] is a switch connected in parallel to the print switch SW, which is turned on and off by a solenoid SOL.1, and a switch CSW2 which is connected to a charging circuit of capacitors C, and C is a rotary switch which is driven by the solenoid SOL.,.

If the number of the copy paper sheets to be copied is set to N, the capacitor C is charged by the current through a contact 35;, of relay RL during the movement of the platform 3. Thereafter with the returning of the platform 3, the microswitch MS is closed to discharge the capacitor C through the contact 38 of the relay RL with the solenoid SOL. retained for a predetermined period of time. At this time. the switch CSW is closed and the same condition as the closure of the print switch SW is provided. At the same time, the retary switch CSW moves one step to sequentially move to a contact of (n I), thus subsequent copying cycles being effected.

Thereafter, the similar steps are repeated, but at the time of the last one sheet, charging of the capacitor C is not performed without subsequent functioning of the solenoid SOL.,, and the copying cycle is over.

For copying by manual insertion, the guide table 23 is opened to its horizontal position with a contact of a microswitch MS, for manual insertion is switched to cut off the circuit for the print switch SW.

Thus, upon manual insertion of the copy paper sheet, leading edge of the copy paper sheet actuates the movable contact arm of a microswitch MSP for manual in sertion to start the copying cycle.

As is clear from the above description, according to the copying apparatus of the present invention, the photoreceptor drum which has particularly required large space conventionally among processing devices constituting the copying apparatus is made optically as small as possible in diameter, so that two or more revolutions thereof completes one copying cycle, while the filter bag is made smaller in size by forming an electric field in the cleaning device to attract and remove most of the residual toner by the electric field, with resultant compact size and light weight of the copying apparatus,

Since the residual toner particles on the photoreceptor drum is adapted to be electrically attracted and collected, the collected toner particles are uniform in electrical characteristics and can be economically reused.

The copying apparatus of the present invention is easy to operate with high accuracy since each of the processing devices is adapted to be started or stopped in timed relation to the movement of the platform by a series of switches to be actuated as the platform for the original reciprocates.

Furthermore, the provision of the central suction device associated with the filter section comprising two sections is very effective in eliminating toner particles scattering in the developing device, those removed by the cleaning device and those floating in various parts of the apparatus, or the heat arising from the fixing device and the exposure lamp, or the poisonous gases generated in the fixing device, thus protecting the atmosphere in the room from pollution.

Although the present invention has been fully described by way of example with reference to the attached drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. One such change would be to allow the optical system to scan in a known manner with the transparent platform kept stationary. Therefore. unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as included therein.

What is claim is:

l. in an electrophotographic copying apparatus of the toner powder image type which has:

feeding means for feeding copy paper into the apparatus,

a horizontally reciprocating transparent platform on which the document to be copied is placed,

exposure lamp means for illuminating the document on said transparent platform,

a rotatable photoreceptor drum for contacting the paper supplied by said feeding means, said photoreceptor drum located under said transparent platform and rotatable relative to a plurality of processing means which are actuated in a timed relation to the rotation of the drum, said processing means including drum surface charging means, developing means, image transfer charging means, erasing means, and cleaning means,

paper discharging means adjacent said image transfer charging means, for discharging the paper after the image has been transferred thereto,

fixing means for fixing a toner powder image onto said copy paper,

suction paper transfer means for conveying paper from said image transfer charging means to said paper discharging means and said image fixing means, and

carrying means for carrying said fixed copy paper out of said apparatus,

an improvement thereof comprising:

an improved photoreceptor drum having a diameter which makes optically possible efficient electrophotographic copying utilizing a plurality of drum revolutions for each copy cycle;

a rotatable metal cylinder rotatably position adjacent said cleaning means;

a corona discharger enclosed within said metal cylinder for producing a strong electrical field on said metal cylinder for attracting and collecting toner particles removed from said photoreceptor drum by said cleaning means;

suction means adjacent said metal cylinder for attracting any remaining toner particles removed from the surface of said photoreceptor drum by said cleaning means which are not attracted to and collected on the surface of said metal cylinder, said suction means also connected to said suction paper transfer means. said exposure lamp means, said drum surface charging means, said image transfer charging means, and said fixing means. whereby scattered toner particles, heat, and poisonous gases produced in these means are withdrawn by the suction means;

filtering means connected to said suction means comprised of:

a first filter section ducted to said cleaning means and said metal cylinder and having mesh openings facing said fixing means and said exposure lamp means;

a replaceable filter medium in said first filter section;

a second filtering section joined to said first filtering section and said suction means to permit the flow of gases therethrough;

mesh screens between said second filtering section and said suction means treated by a catalyst effective for reducing ozone; and

a granular carbon filtering medium in said second filtering section for purifying the gases passing there through.

2. An electrophotographic copying apparatus as claimed in claim 1, wherein said filtering means is further comprised ofa baffle plate extending upwardly approximately half-way in said first filter section at right angles to the bottom of said first filter section with one surface thereof facing the duct opening into said first filter section.

3. A toner powder image type electrophotographic copying apparatus for copying an image onto paper comprising in combination:

a transparent platform onto which an original document to be copied is placed;

an exposure lamp beneath said transparent platform for directing light onto the document to be copied on the transparent platform;

a rotatable photosensitive drum beneath said platform and said lamp;

a photosensitive drum surface charger for uniformly applying charges onto the surface of said photosensitive drum located at the circumference of said drum;

a wire mesh shield above said drum surface charger;

a first erasing lamp means over said wire mesh shield for selectively erasing charges on said photosensitive drum;

scanning means adjacent said drum surface charger at a position along the circumference of said photosensitive drum for scanning the image of the original document onto said drum subsequent to the uniform application of charges onto the drum by the drum surface charger, whereby an electrostatic latent image is formed thereon;

toner developing means adjacent said scanning means at a position along the circumference of said photosensitive drum for supplying toner to the uniformly charged surface scanned by the scanning means, whereby an electrostatic latent image is developed thereon;

toner replenishing means above said toner developing means for replenishing the toner to the developing means used to develop said latent image;

copy paper feeding means adjacent said toner developing means at a position along the circumference of said photosensitive drum for selectively feeding copy paper autom atically and manually into the apparatus;

an image transferring charger adjacent said paper feeding means at a position along the circumference of said photosensitive drum for transferring said developed latent image onto copy paper fed from said paper feeding means;

a wire mesh shield around the bottom portion of said image transferring charger;

second erasing lamp means adjacent said image transferring charger at a position along the circumference of said photosensitive drum for erasing charges on said photosensitive drum after the charged surface passes said image transferring charger;

cleaning means adjacent said second erasing lamp means at a position along the circumference of said photosensitive drum for cleaning the toner from the surface of the drum after the charge has been erased by said second erasing lamp means. said cleaning means comprised of a rotary brush in contact with said photosensitive drum for cleaning the residual toner from the drum after being erased by said second erasing lamp means and rotatable metal cylinder means adjacent said brush chargeable to a high electrical potential opposite in polarity to that of the toner removed by the brush for collecting the toner removed by the brush;

paper transporting means between said image transferring charger and said second erasing lamp means for transporting the copy paper with the toner image transferred thereto from the photosensitive drum by the image transferring charger away from said image transferring charger;

paper discharging means positioned over said paper transporting means for erasing the charges on said copy paper coming from said image transferring means on said paper transporting means;

toner fixing means at the end of said paper transporting means for fixing the toner to the paper which has been discharged by the paper discharger;

paper removing means on the opposite side of the toner fixing means from the paper transporting means for removing the copy paper with the fixed toner image thereon from the apparatus;

suction means adjacent said exposure lamp connected to said cleaning means, said toner developing means, said paper transporting means, and said toner fixing means for removing scattered toner, heat, poisonous gases, and ozone generated by these various means; and

filtering means connected to said suction means for filtering the impurities removed from the various means by the suction means.

4. An apparatus as claimed in claim 3, wherein said suction means is communicated with said exposure lamp for removing heat from said lamp.

5. An apparatus as claimed in claim 3, wherein said filtering means is comprised of:

a first filter section ducted to said cleaning means and having a mesh opening facing said fixing means and said exposure lamp;

a replaceable filter medium in said first filter section;

a second filtering section joined to said first filtering section and said suction means for permitting the flow of gases therethrough;

mesh screens between said second filtering section and said suction means treated by a catalyst effec tive for reducing ozone; and

a granular carbon filter medium in said second filtering section for purifying the gases passing therethrough.

6. An apparatus as claimed in claim 5, wherein said filter means is further comprised of a'baffle plate extending upwardly, approximately half-way, in said first filter section at right angles to the bottom of said first filter section with a surface thereof facing the duct opening into said first filter section 7. An apparatus as claimed in claim 3, wherein said metal cylinder means of said cleaning means is comprised of rotatable metal cylinder positioned adjacent said rotary brush, and a corona dischargcr enclosed within said metal cylinder for producing an electrical field on said metal cylinder for attracting and collecting the toner particles removed from the photosensitive drum by said rotary brush.

8. An apparatus as claimed in claim 3, wherein said copy paper feeding means for automatic feeding of copy paper is comprised of:

a horizontal support means for supporting the sheets of copy paper to be fed into the apparatus; and pivoted spring biased roller means positioned to contact the top sheet of copy paper on said horizontal support means for urging the copy paper into the apparatus by the rotation of the roller.

9. An apparatus as claimed in claim 8, wherein said copy paper feeding means for manual feeding of copy paper is comprised of:

a pivotable guide table mounted above said horizontal support means for guiding the copy paper fed into the apparatus manually;

hinge means connected to said pivotable guide means for movement therewith and for contacting and pivoting said pivoted spring biased roller means away from said horizontal support means when said pivotable guide means is pivoted downward to receive copy paper;

stationary roller means above the surface of said pivotable guide means for contact with said pivoted spring biased roller means pivoted by said hinge means when said pivotable guide table is pivoted to receive copy paper manually. whereby copy paper manually inserted along said pivotable guide table means is urged between said rollers and forced into the apparatus by the rotation of the rollers. 

1. In an electrophotographic copying apparatus of the toner powder image type which has: feeding means for feeding copy paper into the apparatus, a horizontally reciprocating transparent platform on which the document to be copied is placed, exposure lamp means for illuminating the document on said transparent platform, a rotatable photoreceptor drum for contacting the paper supplied by said feeding means, said photoreceptor drum located under said transparent platform and rotatable relative to a plurality of processing means which are actuated in a timed relation to the rotation of the drum, said processing means including drum surface charging means, developing means, image transfer charging means, erasing means, and cleaning means, paper discharging means adjacent said image transfer charging means, for discharging the paper after the image has been transferred thereto, fixiNg means for fixing a toner powder image onto said copy paper, suction papger transfer means for conveying paper from said image transfer charging means to said paper discharging means and said image fixing means, and carrying means for carrying said fixed copy paper out of said apparatus, an improvement thereof comprising: an improved photoreceptor drum having a diameter which makes optically possible efficient electrophotographic copying utilizing a plurality of drum revolutions for each copy cycle; a rotatable metal cylinder rotatably position adjacent said cleaning means; a corona discharger enclosed within said metal cylinder for producing a strong electrical field on said metal cylinder for attracting and collecting toner particles removed from said photoreceptor drum by said cleaning means; suction means adjacent said metal cylinder for attracting any remaining toner particles removed from the surface of said photoreceptor drum by said cleaning means which are not attracted to and collected on the surface of said metal cylinder, said suction means also connected to said suction paper transfer means, said exposure lamp means, said drum surface charging means, said image transfer charging means, and said fixing means, whereby scattered toner particles, heat, and poisonous gases produced in these means are withdrawn by the suction means; filtering means connected to said suction means comprised of: a first filter section ducted to said cleaning means and said metal cylinder and having mesh openings facing said fixing means and said exposure lamp means; a replaceable filter medium in said first filter section; a second filtering section joined to said first filtering section and said suction means to permit the flow of gases therethrough; mesh screens between said second filtering section and said suction means treated by a catalyst effective for reducing ozone; and a granular carbon filtering medium in said second filtering section for purifying the gases passing therethrough.
 2. An electrophotographic copying apparatus as claimed in claim 1, wherein said filtering means is further comprised of a baffle plate extending upwardly approximately half-way in said first filter section at right angles to the bottom of said first filter section with one surface thereof facing the duct opening into said first filter section.
 3. A toner powder image type electrophotographic copying apparatus for copying an image onto paper comprising in combination: a transparent platform onto which an original document to be copied is placed; an exposure lamp beneath said transparent platform for directing light onto the document to be copied on the transparent platform; a rotatable photosensitive drum beneath said platform and said lamp; a photosensitive drum surface charger for uniformly applying charges onto the surface of said photosensitive drum located at the circumference of said drum; a wire mesh shield above said drum surface charger; a first erasing lamp means over said wire mesh shield for selectively erasing charges on said photosensitive drum; scanning means adjacent said drum surface charger at a position along the circumference of said photosensitive drum for scanning the image of the original document onto said drum subsequent to the uniform application of charges onto the drum by the drum surface charger, whereby an electrostatic latent image is formed thereon; toner developing means adjacent said scanning means at a position along the circumference of said photosensitive drum for supplying toner to the uniformly charged surface scanned by the scanning means, whereby an electrostatic latent image is developed thereon; toner replenishing means above said toner developing means for replenishing the toner to the developing means used to develop said latent image; copy paper feeding means adjacent said toner developing means at a position along the circumference of said photosensitive drum for selectively feeding copy paper automatically and manually into the apparatus; an image transferring charger adjacent said paper feeding means at a position along the circumference of said photosensitive drum for transferring said developed latent image onto copy paper fed from said paper feeding means; a wire mesh shield around the bottom portion of said image transferring charger; second erasing lamp means adjacent said image transferring charger at a position along the circumference of said photosensitive drum for erasing charges on said photosensitive drum after the charged surface passes said image transferring charger; cleaning means adjacent said second erasing lamp means at a position along the circumference of said photosensitive drum for cleaning the toner from the surface of the drum after the charge has been erased by said second erasing lamp means, said cleaning means comprised of a rotary brush in contact with said photosensitive drum for cleaning the residual toner from the drum after being erased by said second erasing lamp means, and rotatable metal cylinder means adjacent said brush chargeable to a high electrical potential opposite in polarity to that of the toner removed by the brush for collecting the toner removed by the brush; paper transporting means between said image transferring charger and said second erasing lamp means for transporting the copy paper with the toner image transferred thereto from the photosensitive drum by the image transferring charger away from said image transferring charger; paper discharging means positioned over said paper transporting means for erasing the charges on said copy paper coming from said image transferring means on said paper transporting means; toner fixing means at the end of said paper transporting means for fixing the toner to the paper which has been discharged by the paper discharger; paper removing means on the opposite side of the toner fixing means from the paper transporting means for removing the copy paper with the fixed toner image thereon from the apparatus; suction means adjacent said exposure lamp connected to said cleaning means, said toner developing means, said paper transporting means, and said toner fixing means for removing scattered toner, heat, poisonous gases, and ozone generated by these various means; and filtering means connected to said suction means for filtering the impurities removed from the various means by the suction means.
 4. An apparatus as claimed in claim 3, wherein said suction means is communicated with said exposure lamp for removing heat from said lamp.
 5. An apparatus as claimed in claim 3, wherein said filtering means is comprised of: a first filter section ducted to said cleaning means and having a mesh opening facing said fixing means and said exposure lamp; a replaceable filter medium in said first filter section; a second filtering section joined to said first filtering section and said suction means for permitting the flow of gases therethrough; mesh screens between said second filtering section and said suction means treated by a catalyst effective for reducing ozone; and a granular carbon filter medium in said second filtering section for purifying the gases passing therethrough.
 6. An apparatus as claimed in claim 5, wherein said filter means is further comprised of a baffle plate extending upwardly, approximately half-way, in said first filter section at right angles to the bottom of said first filter section with a surface thereof facing the duct opening into said first filter section
 7. An apparatus as claimed in claim 3, wherein said metal cylinder means of said cleaning means is comprised of rotatable metal cylinder positioned adjacent said rotary brush, and a corona discharger enclosed within said metal cylinder for producing an electrical field on said metal cylinder for attracting and collecting the toner particles removed from the photosensitiVe drum by said rotary brush.
 8. An apparatus as claimed in claim 3, wherein said copy paper feeding means for automatic feeding of copy paper is comprised of: a horizontal support means for supporting the sheets of copy paper to be fed into the apparatus; and pivoted spring biased roller means positioned to contact the top sheet of copy paper on said horizontal support means for urging the copy paper into the apparatus by the rotation of the roller.
 9. An apparatus as claimed in claim 8, wherein said copy paper feeding means for manual feeding of copy paper is comprised of: a pivotable guide table mounted above said horizontal support means for guiding the copy paper fed into the apparatus manually; hinge means connected to said pivotable guide means for movement therewith and for contacting and pivoting said pivoted spring biased roller means away from said horizontal support means when said pivotable guide means is pivoted downward to receive copy paper; stationary roller means above the surface of said pivotable guide means for contact with said pivoted spring biased roller means pivoted by said hinge means when said pivotable guide table is pivoted to receive copy paper manually, whereby copy paper manually inserted along said pivotable guide table means is urged between said rollers and forced into the apparatus by the rotation of the rollers. 